Electronic writeboards or whiteboards (EWBs) are known in the art and have been used in conjunction with host computers executing applications software to provide enhanced multimedia and teleconferencing capabilities. An example of an electronic writeboard of this nature is sold by SMART Technologies Inc. of Calgary, Alberta, Canada under the name SMART Board. The SMART Board electronic writeboard includes a touch sensitive panel, a tool tray accommodating a plurality of tools such as coloured pens and an eraser as well as a driver and an associated controller.
In use, the electronic writeboard is connected to a host processor such as a personal computer operating in a Windows.RTM. environment and executing applications software, via a serial data connection. The electronic writeboard can be operated in one of three modes, namely a projected mouse mode, a projected mark-up mode and a non-projected mode.
In the projected mouse mode, the image displayed on the monitor of the personal computer is projected onto the touch sensitive panel. In this case, the electronic writeboard functions as a giant mouse providing input to the personal computer in response to user contact with the touch sensitive panel. Specifically, the electronic writeboard generates mouse events in response to user contact with the touch sensitive panel, which are conveyed to the personal computer for processing. Thus, by contacting the touch sensitive panel, the personal computer can be conditioned to open and display menus, to activate displayed menus, to drag icons, to execute software and to switch applications by changing input focus. The latter event of course is achieved by contacting the touch sensitive panel outside of the window of the active application running on the personal computer.
In the projected mark-up mode the coloured pens and eraser are used to contact the touch sensitive panel. The active application running on the personal computer tracks where writing and erasing has occurred and maintains a computerized image of what is drawn on and erased from the touch sensitive panel. The computerized image includes one or more objects, each of which represents writing on the touch sensitive panel. The computerized image is projected onto the touch sensitive panel so that the user can see the computerized image.
In the non-projected mode, no images are displayed on the touch sensitive panel. Dry-erase markers are used to contact the touch sensitive panel. The application running on the personal computer tracks where writing and erasing has occurred and maintains a computerized image of what is drawn on the touch sensitive panel. However, since no image is displayed on the touch sensitive panel, the electronic writeboard is not interactive when operated in this mode.
Currently there are two prior art erasing techniques used in electronic writeboards during operation in the projected mark-up mode. One technique is to detect when the eraser touches an object representing writing that is displayed on the electronic writeboard and delete the entire object touched by the eraser. This approach is unsatisfactory due to the fact that the erased area often has little bearing with respect to the location of the eraser on the touch sensitive panel. Also, this technique does not allow part of an annotation represented by an object to be erased.
Another technique, currently implemented by the SMART Board, describes the size and shape of the eraser as a circular mask. When the eraser contacts annotations displayed on the touch sensitive panel that are represented by an object, the parts of the annotations within the circular mask are removed. During movement of the eraser, the mask is repeatedly applied to the object to erase the appropriate parts of the annotations represented by the object. Unfortunately, these erase operations require a significant amount of time to complete and therefore, the eraser may move a large distance during the time a single erase operation is performed. As a result, the mask is applied to the object at spaced locations resulting in disjointed parts of annotations being removed instead of a continuous swatch representing the eraser stroke. It is possible to save the intermediate eraser positions and apply the mask retroactively; however, this results in the erase operations falling further and further behind the actual eraser position. Accordingly, improvements to erase operations in electronic writeboards are desired.
It is therefore an object of the present invention to provide a novel method and editor for erasing on an electronic writeboard.